Boiler tube panel walls, such as those found in steam generating units, typically consist of a multitude of individual boiler tubes that are aligned and secured together. Their structural integrity enables a number of such panel walls to be interconnected and used to define the furnace enclosure of the steam generating unit.
Because of the strength and stiffness of these panel walls, it is common to hang or support other devices from the outside of the panel wall rather than provide a separate support outside the furnace enclosure for such devices. However, one caveat when doing so, is to take into account the high temperature within the furnace enclosure and the consequent expansion/contraction of the panel wall. It is also important that the device being supported by the panel wall not contribute to the corrosion of or structural damage to the individual tubes so as not to cause or increase the possibility of a rupture thereof. Another concern is the desire to maintain an air-tight envelope around the furnace with no breaks therein in order to prevent any ga leakage from occurring either into or out of the furnace enclosure or the supported device.
Currently, whenever a wind box or other pressurized enclosure is attached directly to the backside (cold or casing side) of a tangent tube panel wall, the arcuate area between adjacent tubes is oftentimes filled with a silver solder. This filler material separates the windbox from the furnace and it also insures that no break or gap will occur that would otherwise enable pressurized gas to flow between the two. Additionally, without such a filler in the arcuate area between adjacent tubes, it is possible that air would leak out of the wind box rendering it or other pressurized enclosures ineffective or non-functional for its purpose (e.g. the supply of metered combustion air).
Because silver solder is very expensive, some have tried to fill this area with weld metal instead. However, such substitution has the potential of damaging the individual boiler tubes by burning through the wall of the tube or harmfully altering the tube metallurgy. Additionally, should this gap be large, the accumulated mass of weld metal will alter the physical expansion/contraction and other properties of the adjacent tubes, thereby increasing the internal stresses and strains in the panel wall.
It is thus an object of this invention to provide an efficient and economical manner of sealing the gap between adjacent tubes of a panel wall. Another object of this invention is to provide a means whereby adjacent wind boxes or other enclosures supported by the panel walls do not leak through these gaps thereby reducing their effectiveness. Yet another object of this invention is to accomplish an air-tight seal in a non-corrosive manner such that no damage or alteration of the individual tubes will occur. Still another object of this invention is to fill this gap in such a manner that the material can withstand the high temperatures of the furnace enclosure while not affecting the efficiency of the panel walls. These and other objects and advantages will become obvious upon further investigation.